Field of the Invention
The present invention is broadly concerned with improved magnetic switch assemblies which overcome the tendency of some prior switches to hang up or stick owing to frictional forces encountered during switch operation. More particularly, the invention is concerned with such switch assemblies having a housing with an elongated electrode extending into the housing and having a free end. The electrode includes an enlarged diameter section adjacent the inner free end of the electrode to prevent switch malfunction.
Description of the Prior Art
Prior art alarm systems use magnetic switches attached to doors and/or windows for detecting unauthorized opening thereof. One common type of magnetic switch is a so-called reed switch. This type of switch is subject to unauthorized manipulation through use of an external magnet. That is, an intruder can use a strong magnet held in proximity to the reed switch to hold the switch closed (or open depending upon the control scheme), and thereby open a supposedly protected door or window without triggering the alarm system.
Magnasphere Corporation of Waukesha, Wis. commercializes a specialized type of magnetic switch giving improved performance and protection against external magnet manipulation. Such switches generally comprise a metallic housing with an internal switch ball shiftable between a first position in contact with a pair of switch electrodes and a second position out of such simultaneous contact. Switches of this type are disclosed in U.S. Pat. Nos. 5,977,873 and 7,291,794. Other prior references include U.S. Pat. Nos. 5,332,992, 5,530,428, 5,673,021, 5,880,659, 6,087,936, 6,506,987, 6,603,378, 6,803,845, 7,023,308, RE39,731, 7,825,801, 7,944,334, 8,228,191, 8,314,698, 8,487,726, and 8,648,720, and EP 2638555. In the absence of sophisticated switch ball conditioning, the switch balls of these switches can hang up or become stuck in the simultaneous electrode contact positions thereof, owing to frictional forces encountered between the balls and electrodes. This is a problem which can detract from the utility of the magnetic ball switches.